The present invention relates to a solenoid valve for controlling an injection valve of an internal combustion engine.
German Published Patent No. 196 50 865 discusses a solenoid valve used for controlling the fuel pressure in the control pressure chamber of an injection valve, such as an injector of a common rail injection system. In such injection valves, the fuel pressure in the control pressure chamber controls the movement of a valve plunger with which the injection opening of the injection valve is opened or closed. The known solenoid valve has an electromagnet situated in a housing part, an axially movable armature guided in a sliding piece and acted upon by a closing spring, and a control valve member moved by the armature which cooperates with the valve seat of the solenoid valve and thereby controls the fuel discharge from the control pressure chamber. The armature has an armature plate, and an armature bolt which is supported in a slidingly movable manner in the mechanical guideway formed as a bore in the sliding piece.
In the known solenoid valves the sliding piece has to be manufactured with great precision in order to guarantee optimal functionality of the solenoid valve. The mechanical armature guideway through the sliding piece gives rise to frictional losses, which have to be considered when designing the overall system. In addition to that, fitting the sliding piece into the housing part of the solenoid valve requires a mechanically costly overall construction.
The advantages of the present invention arise by saving the sliding piece which has been used up to the present time, and discontinuing of the production and work steps connected with the sliding piece. Because of the discontinuation of the sliding piece guiding the armature, frictional losses caused by the mechanical armature guideway during opening and closing the solenoid valve are avoided. Because of the discontinuation of the sliding piece, the construction of the armature can advantageously be greatly simplified and optimized from a functional point of view. On account of the simplified construction, the deviation of the dynamic behavior of the solenoid valve is further advantageously reduced, so that the reliability of the overall system is increased. Beyond that, a substantial advantage comes about from the considerable cost reduction during production of the solenoid valve. Thus, not only is the sliding piece omitted, but the armature can also be designed to be less costly, and can be made, for example, as a simple stamped part.
A particularly flat construction method of the armature is achieved by designing the armature as a disk-shaped armature plate, which acts directly upon the control valve member with its side facing away from the electromagnet. Advantageously, in the closed position of the solenoid valve, tilting moments transmitted by the closing spring to the armature are greatly reduced.
Advantageously, armature plate and control valve member are produced as separate components, so that the radially movable armature plate can shift relatively to the control valve member, without the control valve member necessarily being shifted from its centrical position relative to the valve seat. A lateral impact of the control valve member next to the valve seat and a sliding into the valve seat connected with frictional losses are hereby largely avoided.
Especially advantageous is an exemplary embodiment in which, when a current is applied to the electromagnet, the armature may be aligned in the radial direction, by magnetic reluctance forces acting upon the armature, into a centrical position with reference to the centerline of the electromagnet. This can advantageously be achieved if the armature and the magnetic core have geometrical structures situated concentrically about their respective centerline at their mutually facing pole faces, which structures cooperate, when current is applied to the electromagnet, in such a way that the armature is aligned in the centrical position.
Because in the centrical position of the armature its center axis is situated concentrically with the fuel passage, tilting moments acting upon the armature may be further reduced. During the closing of the solenoid valve, the armature meets the control valve member centrically from its centrical position, so that in the closed state of the solenoid valve the control valve member lies centrically on the valve seat for fuel passage, and tilting moments are reduced.